Re: Rapture Session
Continually changing setups may be the source of some of your problems. Maybe simplify the setup to one interface and one controller for while. For example, while the GT-001 can directly connect to the PC, it can also work through the UR22. Yeah, it is having to convert the signal from digital to analog and back but that should not make that big a difference.
Artist places no limit on the number of instruments in a project. That said, there are limits imposed by hardware. Constantly messing with you setup makes it hard troubleshoot and tune the PC for best performance. In addition, programs in Rapture Session vary quite a bit in the load they place on the hardware.
No sound could be a couple of things such as trying to play notes out of range for the particular program or unexpected MIDI data. All the Cakewalk sfz engine synths shut down when they encounter unexpected data. This is often caused by using 3rd party MIDI clips. It can be fixed by removing the offending data from the clips or enabling "Do not intercept NRPNs" in the VST Plug-in Properties found in the VST2/3 drop down above the Rapture Session UI.
Having a track unexpectedly change pitch could be a MIDI routing problem and a failing controller pitch wheel.